The present invention relates to a sprocket intended for use with a motorcycle in noise and vibration which caused when the metal chain and the sprocket body intermesh with one another is absorbed by elastic members of, for instance, rubber.
When a motorcycle is operating, the power transmitting chain generally is strongly vibrated. The chain may merely vibrate mechanically or it may both vibrate and cause noise. There are two kinds of noise which are caused when the chain intermeshes with the sprocket body. The first is a sound caused by contact of the sprocket body and the chain rollers while the second is a sound caused by contact of the sides of the sprocket body and the chain plates.
In order to eliminate the intermeshing noise, a sprocket as shown in FIG. 4 has been proposed in the art. Vibration preventing members b are fixedly secured to both sides of the sprocket body a. For this arrangement, the diameter of the vibration preventing member b is substantially equal to the effective diameter of the sprocket body a and the lower portion of a chain c is in contact with the circumferential surfaces of the vibration preventing members b. As used herein, "effective diameter" is the diameter of the sprocket body measured to the bottom of the teeth along its periphery.
In a motorcycle, the load applied tends to change greatly. As a result, when the load changes from high to low or vice versa, the intermeshing load due to the pulling of the chain greatly changes as a result of which the intermeshing depth is changed. Therefore, in the sprocket shown in FIG. 4, the contact pressure of the chain c on the vibration preventing members b also changes. Accordingly, for a low load, the vibration preventing members b cannot effectively absorb the contact sound which is caused by contact of the sides of the sprocket body a and the chain plates of the chain c. That is, the conventional sprocket cannot provide a uniform noise reducing effect.
Accordingly, an object of the invention is the provision of a sprocket for a motorcycle in which all of the above-described drawbacks accompanying a conventional sprocket have been eliminated.